Antimicrobial active ingredients are used widely in cosmetic deodorants, antidandruff and antiacne formulations, footcare and personal hygiene compositions, and also oral hygiene and dental care products.
Body odor arises primarily when odorless perspiration is decomposed by microorganisms on the skin. Only the microbial degradation products cause the unpleasant sweat odor. This arises, in particular, where there is a high density of sweat glands and also a high density of odor-producing germs, such as, for example, in the armpits.
Certain skin diseases are also associated with excess growth of undesired microorganisms on the skin. Thus, acne is caused inter alia through uncontrolled growth of the anaerobic skin bacterium Propionibacterium acnes. Dandruff is connected inter alia with the fungus Malassezia Furfur. 
In the oral hygiene sector, microorganisms play a significant role, for example in the formation of caries and dental plaque.
The effect of deodorants can be based on various mechanisms which, if appropriate, can also be combined:                avoidance of sweat formation through antiperspirants, such as, for example, aluminum chlorohydrate (ACH) or aluminum zirconium tetrachlorohydrex GLY,        prevention of odor formation through control of odor-forming microorganisms (in particular coryneforms),        prevention of odor formation through inhibition of microbial enzymes which are responsible for odor formation from sweat,        binding of odors which cause sweat odor by substances, e.g., by zinc compounds, such as zinc ricinoleate or salts thereof or by cyclodextrins,        concealment of sweat odor by means of fragrances.1. Antimicrobial Active Ingredients        
The use of antimicrobial active ingredients in cosmetic formulations, in particular in cosmetic deodorants, is sufficiently known from the prior art.
In use, for example, is triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol), which exhibits an antimicrobial effect against a broad spectrum of microorganisms. On account of the broadband effect, triclosan has an adverse effect on the microflora of the skin. Furthermore, due to the specific mode of action, there is the risk of the formation of resistances.
DE 42 40 674 discloses a combination of glycerol monoalkyl ethers of the general formulaR—O—CH2—CHOH—CH2OHwhere R is a branched or unbranched C6-18 alkyl group, with one or more further deodorizing active ingredients as a deodorant composition.
A disadvantage of these compounds is that they only have low solubility in aqueous systems and can only be formulated in such systems in combination with solubilizers. Furthermore, these substances also have a suppressing or germ-reducing effect on typical representatives of normal skin flora, e.g., Staphylococcus epidermidis, as a result of which the microbiological equilibrium on the skin can be permanently disturbed.
WO 02/30383 discloses antimicrobial deodorants which comprise a transition metal chelator as the active ingredient.
DE-A 42 37 081 describes cosmetic deodorants characterized by an effective content of monocarboxylic acid esters of di- or triglycerol. These prior art compounds have a specific suppression on the growth of odor-forming germs, but, on account of the ester bond, only have long-term stability in formulations within a restricted pH range.
EP 0 262 587 discloses N-octyl- and N-decylsalicylamide inter alia as an antimicrobial active ingredient in body deodorants. Other derivatives, in particular those based on aliphatic carboxylic acids, or alkoxylated derivatives are not described.
2. Amides in Cosmetic Formulations
Simple N-substituted lactic acid amides have been known for a long time. For example, Ratchford describes the synthesis of N-alkyl-, N-aryl- and N-alkenylamides of lactic acid (“Preparation of N-substituted lactamides by aminolysis of methyl lactate”, J. Org. Chem. 1950, 15, 317 to 325; “Preparation and properties of N-alkyllactamides”, J. Org. Chem. 1950, 15, 326 to 332) by reacting lactic acid or methyl lactate with alkylamines.
JP2005-060457 describes compounds of the general formulaR1—NH—CO—R2 where R1 is a linear or branched C6-21 alkyl radical, R2 is a methyl, 1-hydroxyethyl or 1-hydroxy-1-methylethyl group, as thickeners in cosmetic formulations. An antimicrobial effect of the products is not described.
DE-A 26 31 284 provides cosmetic compositions with a content of amides of hydroxyalkanlecarboxylic acids of the general formulaR1—CHOH—R2—CONR3R4 where R1═C1-4 alkyl, R2 is a direct bond or C1-3 alkylene (optionally alkyl- or hydroxy-substituted), R3 and/or R4, independently of one another, are C1-4 alkyl or C2-6 hydroxyalkyl having 1 to 5 OH groups.
In the cosmetic compositions of DE-A 26 31 284, the amides serve as humectants. An antimicrobial effect is not mentioned. Furthermore, neither longer-chain nor alkoxylated derivatives are described.
U.S. Pat. No. 3,916,003 describes nonionic surfactants of the formula
where R is an aliphatic hydrocarbon radical having 17 carbon atoms, the polyoxyalkylene chain is bonded at position 12 of the carbon chain, R′ is a hydrogen atom or a short-chain alkyl radical, and y is a number from 1 to 50. Neither N-alkylated nor shorter-chain derivatives are described.
U.S. Pat. No. 4,851,434 describes compounds of the general structure
where R1 and R2 are H or short alkyl radicals, and X corresponds to one of the groups (CH2CH2O)n, (CH2CH(CH3)O)n, (CH2CH2CH(CH3)O)n or CH2(CHOH)4CH2O. The compounds disclosed in the '434 patent are described as humectants in cosmetic formulations. The substances differ in principle from the substances described in this application since the latter contain polyalkylene oxide groups on the amide nitrogen (not on the OH oxygen) and furthermore contain no simple N-alkyl radicals. Moreover, no antimicrobial or bacteriostatic properties are described in the '434 patent as well.